We have removed one of our budget picks, the Paradox long-sleeved top, because the company appears to have ceased operations. If you happen to find a Paradox top for sale, though, it’s still a good base layer for the price.

Your guide

Liz Thomas

In our quest to find the best women’s base-layer top and bottom, we sent seven testers skiing, running, rock climbing, cabin lounging, and more in 18 women’s tops and 17 bottoms for four months. The flattering and odor-resistant Smartwool Merino 150 Base Layer Pattern Long Sleeve handled it all, while the comfy Arc’teryx Rho LT Bottom had the best fit of any long johns we tried.

Buying Options

The Smartwool Merino 150 Base Layer Pattern Long Sleeve is an all-around workhorse base layer: It fits great, stays in place, wicks while you’re working, and warms when you’re taking a break. What distinguished this top from other base layers in our test, though, was its comfort and fit. Our lankiest testers applauded its long sleeve and shirt length, which kept their wrists and backs covered. Testers also liked the shirt’s pinch-free, flattering design. The microweight fabric—made of merino wool fibers spun around a nylon core—was particularly soft, non-itchy, and durable compared with the competition. Despite having perhaps the lightest-weight fabric we tested (at 150 grams/m2), the Smartwool Merino 150 kept us insulated in every temperature, and was beloved among our weight-conscious traveling and backpacking testers.

Because the shirt was so thin, in our tests it felt more breathable (and dried more quickly) than other, similar wool layers. Heat and vapor were able to escape quickly during movement, especially compared with the Hot Chillys and Duofold base layers we tested. Testers noted that even after fall trail runs in Colorado or long, steep climbs in Southern California’s mountains, the Smartwool top breathed well and wicked away sweat, drying with uncharacteristic speed for a wool base layer. Because it breathed so effectively and offered UPF 30 protection, testers were able to wear this base layer as sun protection with the sleeves rolled down even on warmer days. It performed equally well layered under jackets for skiing in Colorado, and it stayed warm when it got wet in the moist Pacific Northwest.

Buying Options

The Cuddl Duds FlexFit Long Sleeve Crew is an attractive base layer that fits similarly to the popular Lululemon Swiftly Tech Long Sleeve Crew—a perennial ath-leisure activewear top—at half the price. Our testers loved the longer shirt length, but the Cuddl Duds top’s best feature is its long sleeves, which go past the back of the hand and come with (bonus!) thumbholes. In our tests, the stretchy, velvet-soft fabric kept the shirt from riding up during movement and made this top ultra-comfortable. However, the lightweight fabric of the Cuddl Duds wasn’t as warm as that of other layers, especially when it became moist from rain or sweat. Multiday backpackers and testers who did not wash it after a single wear complained of odor, too. It’s a good option for non-overnight activities like day hikes or an afternoon of climbing.

Buying Options

The Arc’teryx Rho LT Bottom is everything a pair of base-layer bottoms should be: soft, stretchy, warm, and resistant to shimmying down during activity. This pair doesn’t stick or rub when layered under pants, and best of all, it can work on its own because it isn’t see-through and has a flattering fit. The thick waistband stays up without digging into your belly or rolling over uncomfortably, and the fabric is soft and stretchy without the plasticky feeling of other synthetic base layers. These bottoms are so comfortable that when you get home from a day of play in the cold, you won’t want to take them off. Note that this was the first time we ever recommended a piece of Arc’teryx gear; usually the company’s items are too specialized to be best for most people. But up until now, all the bottoms we’ve tried have had flaws, and this pair—it just doesn’t. We found it genuinely worth the cost for the fit. We had to pry it away from our testers. They really, really didn’t want to give it back.

Buying Options

The synthetic Hot Chillys Women’s Micro-Elite Chamois Tight almost mirrors the Arc’teryx Rho LT Bottom’s ability to move with you throughout the day, for about $20 less at this writing. These Hot Chillys tights aren’t as stretchy and don’t fit as well as the Arc’teryx bottoms, but they don’t ride up or down, which is more than we can say for almost every pair of women’s bottoms we’ve tried over the past two years.

Buying Options

The workhorse of base-layer bottoms, the Icebreaker BodyfitZone Zone Leggings were among the best of the bunch in our tests. We liked the fit, the mobility, and most of all, the breathability of this pair of bottoms. Plus, merino wool has natural anti-odor capabilities—and for us, it worked. The downside: Merino can be expensive, this pair isn’t as flattering, and it wears more like long underwear than an opaque legging.

Why you should trust us

I’ve hiked more than 15,000 miles on long trails, and I once held the women’s unassisted speed record on the Appalachian Trail (then, 2,181 miles from Georgia to Maine). Over the past nine years, I’ve tested dozens of base layers and taken them from new to threadbare. I’m just as likely to wear them in the office or to a party as I am on the side of a mountain. I am also the instructor of Backpacker magazine’s online Thru-Hiking 101 class, and the author of Long Trails: Mastering the Art of the Thru-Hike.

The author, backpacking the 746-mile-long Great Divide Trail in the Canadian Rockies. Photo: Naomi Hudetz

In addition, I interviewed Justin Lichter and Shawn Forry, the first and only people to hike the 2,650-mile Pacific Crest Trail in the winter, and pioneers of several 1,000-plus-mile treks in places like New Zealand and the Himalayas. In the offseason, Lichter is a ski patroller and Forry is an associate director for Outward Bound. I also spoke with Alli Noland, who has worked for almost a dozen base-layer companies, including the heavy hitters. At the time of our interview, Noland did not represent any of the companies we considered, but she has since gone on to represent Trew. She told us which features distinguished notable base layers in her two decades of public relations (and outdoor) experience. We also picked the brain of designer Outi Pulkkinen from Duckworth to learn how fit could impact the performance of a base layer. To better understand fabric technology such as wicking and anti-odor treatments, we spoke to Pierre Kim, SVP of product development and sourcing at Rhone, a men’s-only activewear company with a line of base layers. Lastly, we talked with Robert Thomas (no relation to the author of this piece), senior apparel product line manager at Smartwool, who talked to us about base-layer fit and core-spun yarn technology.

Should you pick the women’s version?

The best base layer for you will be the one that fits the dimensions of your body and has a design that you are comfortable wearing. Women’s tops are generally designed to account for (and sometimes flatter) stereotypical female curves. If you don’t have curves or don’t want to wear something that exaggerates them, you might opt for a top with a straighter, looser, or boxier cut, or something we highlight in our guide to men’s base layers. Our female testers found the Kora Shola 230 Crew—which we tested but was not a pick—to have a straighter, more gender-neutral fit.

Our 110-pound and 130-pound male-identifying testers picked the women’s tops over the men’s tops because they were more formfitting (which is the ideal fit for a base layer).

Depending on your height and weight, you may find either a men’s or women’s top to be a better fit. Our 110-pound and 130-pound male-identifying testers picked the women’s tops over the men’s tops because they were more formfitting (which is the ideal fit for a base layer). Taller women might opt for a men’s base-layer top because such designs are long enough to prevent an exposed lower back.

Where we tested

Part of the group of base-layer testers, snowshoeing and skiing near Trout Lake, Washington. Photo: Kate Hoch

A good base layer (also known as thermal underwear or long underwear) is an article of clothing that most outdoorspeople will live in from fall until spring. From hiking in cool and dry areas to skiing and snowshoeing to winter rock climbing, our testers played hard in these tops and bottoms in many varying climates—and then wore them some more.

We took these pieces on the following activities and excursions:

Mountaineering Colorado’s fourteeners and the Colorado Centennials (the top 100 tallest peaks in the state) in the winter, spring, and summer

Thru-hiking the Pacific Northwest Trail, a 1,200-mile-long backpacking trip from the Continental Divide in Glacier National Park to the Pacific Ocean in Olympic National Park

Backpacking the GR20, a 112-mile-long route across the island of Corsica, France

Day hiking and backpacking in Boulder’s Open Space and Mountain Parks, including the Skyline Loop Traverse, a popular five-peak suffer-fest traverse of the mountains outside of Boulder, Colorado. Variations of it have been covered by every running and outdoor magazine out there, and it’s the ideal place for testing gear. Our route had at least 6,000 feet of elevation gain, stretched over 20 miles, and had us sweaty even in November.

Day hiking in the San Gabriel Mountains, including the Sheep Mountain and Cucamonga Wilderness, in California: This mountain range, including the 10,000-foot Mt. San Antonio, features hiking trails at altitude with guaranteed wind. We tested layers on about 10 trips, including on the 30-mile, nine-peak San Gabriel traverse.

Day hiking on the Backbone Trail, Santa Monica Mountains National Monument, California: On this newly designated 67-mile-long trail in the coastal range, a national monument, we hiked 25 miles to add midwinter mild temperatures to the mix.

Exploring Nikko National Park and the shrines and temples of the Nikko UNESCO World Heritage Site, Japan

Sleeping, lounging, and conversing at my grandparents’ house in the mountains of Japan, built in 1910 of wood with no insulation or heating

Spectating a football game in Denver in December, at 10 degrees Fahrenheit

Backcountry skiing in the mountains outside of Silverton, Colorado

Downhill skiing at Colorado’s Loveland Ski Area and Purgatory Resort

Hanging out on the beach at night in Treasure Island, Florida

How we picked

Photo: Rozette Rago

The term base layer often gets used interchangeably with the terms long underwear and thermal underwear, and you’ll find that people usually mean the same thing when referring to any of the three. For this guide, we looked at base layers that functioned as more than just underwear and worked as both a thermal layer and a wicking layer. That way you can stay warm whether you are working up a sweat, sitting around the campfire, or occupying that cold transition time in between. Fit and comfort are the most important factors. A good base layer should be formfitting, shouldn’t hold an odor, and should layer well under ski pants and boots (snappy style helps too).

To supplement what we read, we talked to dozens of outdoor-garment buyers to get their opinions on what they used in the backcountry. The inclusion of Lululemon might surprise you, but we had found that many John Muir Trail hikers (all women) were trying to stretch their dollar by using yoga wear as a base layer on the trail. This is a phenomenon documented by REI, which featured a blog article suggesting that yoga-style pants will work for about 50 percent of people enjoying the outdoors.

Because many outdoor enthusiasts look to stretch their buck by choosing activewear that works indoors, outdoors, and as a style piece, we wanted to test whether yoga wear could hold up to the standard outdoor-apparel competition. In a previous guide to base layers, we made the Lululemon All the Right Places Pant II our pick for women’s base-layer pants, giving credence to the idea that general activewear performs just as well in many outdoor activities and situations. While we still love those pants, this time we found the more traditional base-layer bottoms, the Arc’teryx Rho LT, to function better as a thermal, wicking, and layering piece than the Lululemon pants.

When we began picking models to test, we eliminated those made with cotton and cotton blends immediately. While such pieces work well enough as thermals when dry and are good at wicking, cotton is not an effective insulating layer when wet (either from sweat or rain). Worse yet, cotton takes so long to dry that it makes wearers feel colder than if they were wearing nothing. Wet cotton is also more likely to cause chafing and rashes than other fabrics. By banning cotton from our review, we cut out common brands like Hanes and Fruit of the Loom (the least expensive options available). We then concentrated on brands and performance fabrics meant for outdoor exercise.

We also included several brands better associated with fashion or athletic wear than with the outdoors, such as Under Armour, Cuddl Duds, and Uniqlo.

Cotton takes so long to dry that it makes wearers feel colder than if they were wearing nothing.

For this guide, we leveled the playing field by testing items with as similar design features as we could find (read: basic crewneck, long-sleeve tops without frills). Last time, we tested base-layer tops with all sorts of elements—hoods, half-zips, thumbholes in the cuffs, and pockets. Some of these extras made certain base layers more desirable than the standard long-sleeve top, while an occasional poorly executed detail disqualified an otherwise great base layer. This time around, in order to arrive at the best base layer, we believed it was optimal to compare layers that were—at least superficially—designed the same way for the most part. Another benefit of focusing on crewneck base layers is that they are more affordable than their hooded counterparts.

We also traded out midweight tops for lightweight tops, because we had discovered that definitions of midweight varied more widely by company than for lightweight fabric. By testing lightweight layers, we were able to better determine which fabric had the best warmth-to-weight ratio versus which one was simply the heaviest.

With our chosen layers in hand, our seven testers hiked, skied, snowboarded, mountaineered, and climbed their way through four months of testing. Nearly all of our testers had thru-hiked a 2,000-plus-mile trail at minimum—an experience that requires living in the same base layer from four to six months—so they had opinions. They subjected a few of our top-ranked base layers to hundreds of miles of use on similar trips. Our group of female testers ranged in size from 5′2″ to 5′8″ and 120 to 150 pounds, mostly wore size small or medium, and represented a diversity of body shapes. Some lived and worked in base layers, while others loved layers for casual hiking and day-to-day wear.

Our testers took these base layers to extremes in Colorado, California, Oregon, Washington, Japan, and Florida (why not?), focusing their attention on several key issues.

Fit: Long johns keep you warm by trapping heat in the small gap between your skin and the base layer. This gap allows you to keep a relatively consistent temperature, like being in your own temp-regulated bubble, because the base layer thermoregulates, releasing warm air when the temperature rises and keeping you warm when the mercury dips. The key is to make sure that gap is the right size. Winter-adventuring duo Justin Lichter and Shawn Forry suggested that a base layer should have a relaxed form fit—trim enough to layer over without being bulky. It should not hang off loosely from any part of your body.

Shawn Forry, who taught dogsledding in -40 °F winters in Minnesota for Outward Bound, cautioned against base layers that were too tight. “If the gap between the garment and the body is lost because the layer is too tight, it doesn’t regulate temperature of your skin as well,” Forry said. He clarified, “[C]ompression layers minimize muscle fatigue but don’t work in as wide of a range of temperatures. A tighter fit can constrict circulation, so the body feels colder.”

Base layers work by switching from a wicking layer when you are active to a thermal layer when you are taking a break in the cold.

Exposed skin: We asked testers of varying heights and body types whether the design of the layer left any body part feeling naked. Alli Noland, an outdoor public relations specialist who has represented more than half a dozen companies, said, “Anywhere your veins and arteries come closer to the surface of your skin—like wrists, ankles, the back of your neck, back of your knee, and the surface area of your head—is where it’s really easy to lose heat.” Another issue is the waist. “If it is too tight around the waist, your base layer creeps up,” Justin Lichter advised. “But, if it is too loose, you get bunching.”

Comfort: Does the fabric feel soft, stiff, or plasticky and wetsuit-like? Does it allow a full range of movement? Is it scratchy? Does it make you itch? Forry said it straight: “Since a base layer is right against my skin, comfort is the most important thing I look for.”

Seams: Quality seams don’t just ensure the longevity of your gear—they also can make your long johns feel more comfortable. Noland said, “If seams are too pronounced, there can be rubbing issues—especially if your seams are in the shoulders and you’re wearing a backpack.” Noland suggested paying special attention to the seam around the cuffs: “You’ll feel any pronounced seam all day. The more minimal, the better it will feel.”

Breathability: This term refers to a base layer’s ability to allow water vapor and extraneous heat to pass through the fabric. Some base layers up their breathability with mesh-like panels in key hot-spot areas, such as the armpits. All the base-layer fabrics we tested were breathable, but some were more breathable than others.

Wicking: In addition to allowing water vapor to escape through breathable fabric, base layers help the body regulate temperature by wicking moisture (drawing it away) from the skin and spreading it to a broader surface area to evaporate faster. The more quickly your layer dries out, the less likely you are to feel cool and clammy while moving, or when you stop moving. Wickability depends a lot on fit. “The more contact your base layer has with your skin, the more it can wick moisture away,” Lichter suggested. Merino wicks naturally, but as Noland explained, this isn’t the case with synthetics: “Synthetics don’t wick by themselves. There is nothing in the fiber that gives it that feature. They need a treatment.” Synthetic fibers such as polyester or nylon are hydrophobic, meaning they repel water. That’s one reason they dry quickly. But they won’t naturally pull sweat away from your skin. When a manufacturer treats these fibers on the outside of the garment with a hydrophilic or water-loving topical treatment, the synthetic fabrics start attracting water away from the skin and toward the outer layer of the fabric. Hydrophilic treatments absorb water and disperse it to a greater surface area to reduce evaporation time. These treatments turn the synthetic fabric into a moisture-wicking layer but can wash out of the garment over time. Manufacturers can also make synthetic base layers moisture-wicking by blending hydrophilic and hydrophobic fibers, a process that tends to be more permanent. The better your layer wicks, the less cold you will feel from sweat when you stop being active.

Drying time: Once moisture has wicked away from your skin and into the fabric, it should disperse across a wider surface area to help the layer dry out faster. As Forry said, “Once you establish a dry microclimate between your skin and the base layer, this will increase the effectiveness of your base layer to transition from a moisture-wicking layer to a thermal layer.”

We tested drying time by running all the layers through the wash and hanging them up. We ordered the layers based on how moist they felt right after the spin cycle. Then, every five minutes, we rearranged the order based on moistness until all the layers were dry, recording how long each layer took to attain dry status. We did this test inside a garage, outdoors at night, and outdoors during the day, and got comparable results for each testing period.

Temperature: This one seems obvious, but it can be a little tricky because a base layer needs to keep you warm in a variety of temperature-changing situations. Base layers work by switching from a wicking layer when you are active to a thermal layer when you are taking a break in the cold. They also need to work during the transition time in between. We asked our testers whether the fabric kept them warm (but not too warm) in all three situations and expressed heat when it wasn’t needed.

Durability: We asked our testers, “Will this bottom last just a season or will it hold up to years of love and abuse?” We also asked our testers whether they noticed rips, tears, loose threads, or pilling in the layers they tried.

Odor: Wool has natural antibacterial features. Many synthetic brands add proprietary anti-odor coatings, such as Lululemon’s Silverescent, which uses silver’s natural antibacterial properties to control smell. We asked testers, “After a full day of skiing, can we still roll up to the lodge and not disgust the other guests?”

Style: Is the piece stylish enough to wear alone, or do you always need to wear this underwear under something else? Can it work as an athleisure or athletic-lifestyle fashion accessory in addition to a performance piece? Noland summed up the role of style in base layers: “Ultimately, people are going to reach for the base layer that fits best, keeps them warm, and looks the best.”

Value for price: High-end (and high-price) base-layer fabrics include cashmere, mohair, and alpaca wools. These materials tend to have higher tensile strengths, feel less itchy, and be less absorbent. We didn’t include them in the lineup because most buyers aren’t reaching for those fabrics. The average long john retails just short of $100, and our choices reflect the pieces that are a good deal for the money.

Bonus points: Sustainability is increasingly at the forefront of the outdoor industry’s mind—a trend driven by shoppers. We kept our eyes peeled for American-made long johns, as well as companies that offered recycling or take-back programs for used gear. We also thought about ethics in the manufacturing process. People care about the treatment of the sheep raised for wool more than ever. So we tracked suppliers’ treatment of animals along with each brand’s history of being fair to its labor.

What’s better: Synthetic or wool?

Base layers work by supplementing the body’s natural warming and cooling systems. When you’re inactive, the base layer functions as a thermal layer that traps heat between the fabric and your skin. It creates a warm microclimate, like a thin, personal temperature-regulated bubble. When it’s very hot outside, that temperature-regulated bubble can be cooler than the outside ambient temperature—so a base layer can actually be cooling, too.

When you’re active, you don’t need that thermal feature as much—you need a layer that will dump excess hot air. But when you’re inactive, it’s important that the base layer thermoregulates to keep you warm, because sweat (and other moisture on the skin) draws heat away from the body as it evaporates. And according to this article from Snowshoe Magazine, the body’s cooling system is really effective: “Sweat sucks heat away from our body 25 times faster than does the air; wet skin cools 25 times faster than dry skin.”

“Where this process falls short is the transition time between strenuous activity and stopping,” adventurer Shawn Forry explained to us. “When we take a break, the body is not generating the same level of heat and output.” And all that sweat can leave you feeling cold and wet. So the other job of a base layer—besides warming and cooling—is to wick sweat away from your skin to keep you from feeling chilled.

The most common base layers available are made of wool, synthetics (like polypropylene, polyester, or “proprietary blends”), or a mix of both. Which fabric makes the best base layer is an age-old debate in the outdoor sphere. Wool and synthetics each have their advantages and disadvantages. Blends aim to the capture the benefits of each one, but also have their drawbacks.

Which fabric makes the best base layer is an age-old debate in the outdoor sphere.

The days of scratchy or itchy wool outdoor garments are gone. Base layers these days are made of soft merino wool or a Rambouillet wool (both of which are named after their respective sheep breeds) specifically treated for use right against the skin. Wool has much-noted antibacterial and antimicrobial properties that resist absorption of the short-chain fatty acids in sweat that cause odor.

Wool fibers are naturally stretchy, which makes the fabric feel formfitting and look flattering on a wide variety of people. Unlike synthetics, merino wool naturally wicks sweat away and breathes well (after all, sheep use it to regulate their temperature, too). Although wool doesn’t dry as fast as synthetic materials, it insulates better and feels warmer when damp or wet. If a spark jumps out of your campfire, the wool layer will resist it better than the synthetic (which will likely melt). Most of our testers agreed that wool offered more warmth than synthetic options of comparable thickness and weight, which makes it perfect for less sweaty adventures like downhill skiing and snowshoeing.

Generally, the finer the wool (fewer microns), the more easily the yarn will bend and flex as you move, meaning it will feel less coarse and itchy. In the industry, wool is expressed by the diameter of the fiber in microns, but most apparel companies don’t make that information available to shoppers. It’s safe to say that most wool in apparel is less than 20 microns; traditional wool sweaters, blankets, and carpets are made of thicker wool fibers.

The biggest advantage of synthetic fabric over merino wool is its quick drying time. In our drying tests, the synthetics came out of the spin cycle dry, whereas the wool and blends took almost an hour to lose moisture. What this means for outdoor athletes is that synthetics wick more efficiently than wool—they pull sweat away, and it evaporates faster. If you’ll be sweating a lot in a high-intensity activity like running, synthetic is the way to go. Synthetics are also 30 to 50 percent less expensive than wool or wool blends. Gram-counting backpackers may find that lightweight synthetics have an advantage over heavier wool.

Synthetic-merino blends aim to get the benefits of both fabrics while offering a high-quality base layer at a good price. Of course, these blends often also come with the negative features of their parent fabrics—odor retention, reduced insulation, and long drying times. Our top pick, the Smartwool Merino 150, is constructed of an 87 percent wool and 13 percent nylon fabric made of a yarn constructed of merino wool spun around a nylon core. We reached for blends when doing endurance activities like backpacking and mountaineering because we wanted the thermal qualities of wool plus the durability of synthetic.

Which is more sustainable?

The Sustainable Apparel Coalition created an index to rank the environmental friendliness of various fabrics used in outdoor clothing, including base layers. It takes into account the social and labor impacts of outdoor wear, as well as the life cycle of the piece (including what happens to it after it wears out). According to an SAC member I spoke to, which fabric—synthetic or wool—is “more sustainable” is not a clear-cut issue. Some scientists argue that, as a natural fiber, wool is more sustainable than synthetic materials because synthetics are made of petrochemicals. Other scientists argue that synthetics are more sustainable because they are recyclable and their manufacturing process has a lower carbon footprint than wool’s process. Apparel makes up 10 million tons of waste in landfills each year. The process of manufacturing base layers—regardless of how sustainable it is—leaves an impact on the environment. The most sustainable choice you can make is finding one or a few base layers you really like and wearing them for a very long time.

The SAC also tracks the ethics and labor-supply policies of outdoor-apparel companies. Brands that use wool in their base layers have been criticized for sourcing from farms with reported animal-welfare issues. Meanwhile, the relationship that outdoor-apparel companies have with their labor and suppliers is an ethical issue for both synthetics and wool, because regardless of the fabric, someone has to sew these garments. The 2018 International Trade Union Confederation Global Rights Index can be a source of information about the work conditions the sewers face based on where the garment was constructed or where the fabric was woven at the country level. If environmental, ethical, or animal-welfare concerns influence how you shop, be sure to read up on the brands highlighted in this guide. Some have better track records than others—we’ve noted when brands have good reputations.

Ultimately, the base layer you choose should have the fabric you find most comfortable. Some people are allergic to wool. Others may find synthetics scratchy. Look for a fabric that feels soft and that has a texture you like.

Buying Options

The Smartwool Merino 150 Base Layer Pattern Long Sleeve handles the outdoors like a champ and is so comfortable and flattering, you won’t want to take it off. Made from merino wool spun around a tough nylon thread core, this machine-washable and machine-dryable, odor-resistant shirt is a practical choice if you want to own only one base-layer top. With UPF 30 protection, it’s a favorite to wear by itself during summer hiking or backpacking, but the thin, microweight fabric layers well in cooler weather, too.

When dry, the Smartwool Merino 150 works well as a thermal layer despite its light weight. One tester marveled, “I stupidly wore this long-sleeve base layer on an uphill slog in Southern California and expected to overheat, but it was actually cooling. Then I took a break in the shade at the top of the mountain in the wind, and after the surprisingly quick dry time, it was warm!”

Because this shirt was thin with unobtrusive flatlock seams, it layered well in cooler temperatures without chafing us. The raglan sleeves, stitched in the same way as on a baseball shirt, prevented rubbing or chafing when we wore it with a backpack, and increased our mobility when we went rock climbing.

The raglan sleeves on the Smartwool Merino 150 prevent the seams from rubbing your shoulders when you have a pack on, and give it a more flattering look. Photo: Rozette Rago

The top’s cut is meant not only to be functional but also to make you look good. According to Smartwool’s website, design features like the rolled-back shoulder seams both increase mobility and create the appearance of better posture and a taller figure. So-called “body enhancing lines” narrow from the waist to the hip, creating a slimming effect on the waist and butt. These tailor tricks work: Our testers found the Smartwool Merino 150 to be flattering on the mountain as well as back at the lodge.

The current model is made of 87 percent merino and 13 percent nylon. Generically called “core-spun,” this type of thread uses a two-ply yarn that wraps merino wool around a thin core of nylon. The result is a garment that offers the benefits of wool directly against the skin, plus the strength and resilience of nylon. In Smartwool’s own tests, core-spun yarn proved to be 30 percent more durable than the merino in the company’s 2016 model. Our testers found base layers that used core-spun yarn to be lighter, stretchier, and softer against the skin than many of the other fabrics we tested, including the merino in the fall 2016 model.

Unlike many other outdoor brands, Smartwool offers a 100 percent satisfaction guarantee that allows you to return the shirt (or almost any of the company’s items) within two years regardless of where you bought it.

As with any good base layer, the Smartwool Merino 150 is meant to be formfitting, but not to cut off circulation or feel like a wetsuit. It is loose enough to allow mobility and to hide a muffin top, but tight enough to feel like a second skin under layers. All our testers commented that the sleeves were long enough to cover their wrists well, although almost all the testers also lamented the lack of thumbholes. It was long enough to keep their torsos covered when they reached for a rock-climbing hold, with only Under Armour offering longer shirts.

Reviewers on Amazon and the Smartwool website say that the fit of the Merino 150 is looser than other Smartwool shirts or other models of the Micro 150, which Smartwool has sold since 2004. I confirmed by comparing it against my almost 10-year-old Smartwool microweight shirt: This model is significantly less formfitting. Reviewers on Smartwool’s website also note that it fits more like a T-shirt than the tighter, heavier-weight version, the 250, and that the fit doesn’t match the way it looks online. Our testers preferred the somewhat looser fit, especially compared with the skintight fit of the Duofold by Champion Brushed Back Crew.

Many of the layers we tested this time had a looser fit. While it appears to be a fashion trend, it’s also an improvement in functional design. Outi Pulkkinen at Duckworth told us, “For wool, in general, it actually does perform best when not stretch[ed] tight on skin—the insulation layer between fabric and skin works in hot/sweaty and cool/dry conditions and can enhance [the] drying and insulation factor of the garments[’] performance on that level.” Robert Thomas, senior apparel product line manager for Smartwool, commented, “The 2016 model has a little more merino, so shrunk a little more in the wash [than the current model]. We didn’t change the specs too much, but it did change to fit to consumer expectations to still be relevant to the average body size and shape.” The good news is that everyone in our test group thought they looked better in the slightly looser design.

Photo: Rozette Rago

Our top pick: Flaws but not dealbreakers

Our major reservation about the Smartwool Merino 150 Base Layer Pattern Long Sleeve is its long-term durability. The shirt is very thin. With the fall 2016 model (which Smartwool did not construct with the nylon-core technology), after two months of use, the stitching on the elastic along the sleeve has become loose. Amazon reviews also voice concerns about this downfall.

Because the current model is a redesign that eliminates the faulty elastic around the sleeves, we’re cautiously optimistic about its durability, and our optimism appears to have been justified: Our long-term testers report no undue wear or pilling. Several testers and other people we interviewed found the shirt to have impressive longevity: One individual hiked the entire 2,650-mile Pacific Crest Trail and half the 3,000-mile Continental Divide Trail in one microweight Smartwool shirt. Another started seeing holes about halfway into a thru-hike of the PCT. Both testers, however, said the shirt performed so well that it was well worth the investment, even if they had to buy a new shirt when they finished.

Buying Options

It seems like every outdoor or fitness company has a synthetic base layer these days, but none seemed to fit our testers as well as the Cuddl Duds FlexFit Long Sleeve Crew, a top from a budget brand available at department stores like Macy’s and Kohl’s. We were impressed that a functional, flattering design—including a reinforced neck, thick cuffs, and thumbholes—was available at such an affordable price. We found the fit and design to be similar to that of Lululemon’s popular Swiftly Tech Long Sleeve Crew, which we also tested, but for about half the price. As with the Lululemon top, we discovered that this base layer worked best for high-intensity sports, for short-term outdoor activities like runs, and for warmer, dryer conditions, because it didn’t dry quickly.

What made the Cuddl Duds FlexFit crew our synthetic pick was its fit. The shirt was sufficiently long in our hands-above-head test, and the sleeves were long enough to always keep the wrist area covered, especially when we were using the (much-beloved) thumbholes. The cut of the neck is flattering, showing more collarbone and sternum area but not enough to make you feel cold. In our tests, no part of the top squeezed, constricted, or hung loosely—the fit was just right, no matter the size or shape of the tester.

Thumbholes for the win on the Cuddl Duds FlexFit Long Sleeve Crew. Photo: Rozette Rago

The Cuddl Duds FlexFit’s material is a polyester-spandex blend that is stretchy and soft. The reinforced spandex kept the shirt from riding up during movement in our tests, and we like that it’s lightweight—Cuddl Duds uses a technology in which the polyester thread is hollowed out at its core and reinforcement in the spandex keeps it durable. The fabric wicked away moisture well for us, and was warm and comfortable in dry conditions. However, the amount of spandex made this base layer slower to dry than other synthetics we tested. As a result, testers noticed that it felt cold and clammy when they were testing it in moist conditions such as in Washington’s Columbia River Gorge.

Unlike with the Lululemon top, Cuddl Duds does not advertise an odor treatment for this shirt’s fabric. In our tests, multiday backpackers and those who did not wash it after a single wear complained of a smell.

Because this layer is not as warm as others we tested, it is best suited for situations where you will not be outside for extended periods of time or will be in warmer, dryer conditions. Our testers enjoyed this layer for yoga, runs, or downhill skiing when they would return to warm, indoor conditions shortly after. The testers who took this Cuddl Duds top on hikes on cooler, misty days found that it did not thermoregulate as well as the competition. One long-term tester has reported that although she likes wearing the top, the stitching on one of the seams came unraveled pretty quickly.

Buying Options

When our testers tried the Arc’teryx Rho LT Bottom, they instantly knew that this was what a base-layer bottom was supposed to feel like. The stretchy fabric moves with you and stays flush against your skin but doesn’t squeeze or constrict your legs. The waistband elastic doesn’t slide down your derriere as you ride the chairlift up and ski down the mountain. The soft, almost fleece-like fabric doesn’t bunch or feel plasticky. It wicks away sweat while keeping you warm, all without feeling bulky. The result is a pair of base-layer bottoms that is so comfortable, you’ll want to wear it on the mountain, on the trails, in the lodge, and also to bed.

The fit of the Arc’teryx Rho LT Bottom had more than one leg up over the competition. It doesn’t hug you like a yoga pant or a traditional tight, but it doesn’t hang loosely, either. What impressed us is that it managed to offer a fit that was flush with the skin—not too tight but not too loose. Usually, a bottom works for one body type and not on everyone. But among our testers, from the bigger bootied to the skinny legged, the Rho LT Bottom fit a variety of body shapes. The gusseted crotch and side panels along the leg made a difference not just in sizing and look, but also in movement: Our testers felt much more mobile in this pair than in many of the other bottoms we tried.

The high-rise waistband on the Arc’teryx Rho LT Bottom is meant to cover the lower back. Photo: Rozette Rago

The fabric on the Arc’teryx Rho LT Bottom is notable, too. The fleece lining felt soft against our testers’ skin, while the brushed polyester exterior slid well when layered under pants. But most notably, this pair never felt plasticky, unlike a lot of the bottoms we tested. The weight of the fabric is thin enough to breathe but thick enough to keep you decent (when worn alone) and, more important, warm. A lot of the bottoms we tried had fabric that bunched in the area behind the knees. That’s not a problem with the Rho LT Bottom. Instead, it has just the right amount of stretch to move with you—and your knees. Flat seams prevented the rubbing, chafing, and itching that our testers experienced with other bottoms.

The Arc’teryx pair had the softest, widest waistband of any bottoms we tested except the Lululemon—but without the tight, yoga-pant-like feel. “Waistband” may be a bit of a misnomer on the Rho LT Bottom, though. It’s more like a waist panel, designed to ride high so you don’t lose heat from the small of your back, even if your shirt rides up. This unusual waistband ensured that the bottoms never felt like they were falling down—regardless of the shape of our tester or where our tester wore it on the waist. Unlike the Lululemon pant, the Rho LT also never felt like it was sucking us in. Our snowshoeing tester found them so comfortable and versatile that she used the same pair during a day in the snow on Mt. Hood, while hanging out in the backcountry hut, and then when she was wrapped in her sleeping bag at night.

Our bottom pick: Flaws but not dealbreakers

Aside from the Lululemon piece, this Arc’teryx bottom is the most expensive synthetic base layer we tested. But we’ve tried so many poor-fitting base-layer bottoms, we think that investing in a pair you actually love is worth it. Like many synthetics, this pair retained odor more than the wool pairs we tried, but it does have an anti-odor treatment.

Buying Options

If you’re willing to have a slightly less flattering fit and give up a little comfort, the Hot Chillys Women’s Micro-Elite Chamois Tight offers many of the same features we love about our top pick at a more affordable price. Like the Arc’teryx pair, this bottom has a waistband that stays up when you move. The fabric—while thicker—also doesn’t bunch or hang loose, staying flush against the skin without constricting the body anywhere. In fit and comfort, the Hot Chillys model was leaps ahead of similarly priced bottoms. And unlike most of the base layers we considered, this one is made in the US.

Our snowshoeing tester loved that even when she sank in deep snow near Trout Lake, Washington, these bottoms stuck in place on her waist. But as with most base layers, our testers didn’t want to hang out in this pair after they’d come back inside after a day of play, because the fabric wasn’t that soft.

Our grumbles: The design doesn’t have quite as many side panels along the legs as on the Arc’teryx pair, so movement is slightly more inhibited, and these bottoms aren’t as flattering. The fabric, while still pretty soft, feels more plasticky than the material of the Arc’teryx. Straight out of the box, this pair had a strong factory odor that subsided with a washing. But like all synthetics, this material won’t hide body odor as well as wool.

Buying Options

If you’re looking for a natural-fiber base layer, our testers found the Icebreaker BodyfitZone Zone Leggings to wick, stretch, and move the best during exercise—without the stink factor of a synthetic. The BodyfitZone pair is designed to breathe well, with strategically placed mesh paneling in areas of the body that can overheat, like the back of the knee—a difference that our testers could feel during some winter mountaineering outside Great Sand Dunes National Park in Colorado. But like all the wool pieces we considered, this pair is expensive. We believe wool is worth the extra cash because it is naturally antimicrobial, so it doesn’t retain as much odor as synthetic fabric. Performance—not style—is the priority here. That’s why these Icebreaker bottoms look more like traditional long underwear than almost any other pair we tested. Depending on how you roll, you may not want to wear this pair in public without pants.

While overheating in long johns was often a problem with the bottoms we tested, these leggings seemed designed for people on the move. The mesh paneling, the gusseted crotch, and the natural stretch of merino didn’t restrict our testers from doing outdoor yoga on chilly mornings, though our pick was still stretchier. As on many of the layers we tested, the waistband was a simple 1-inch piece of elastic—a design that was problematic in other layers because it rolled over and dug into our bellies or wouldn’t keep the pants up when we bent down. Somehow, our testers never had issues with this pair’s small waistband leaving them indecent.

Our testers noted that the Icebreaker size medium tended to be slimmer and shorter than other brands’ mediums. If you’re on the cusp of two sizes, we recommend sizing up.

Like all the merino wool pieces we tried, the BodyfitZone Zone Leggings did not dry as fast as the synthetics. This indicates that their moisture absorption rate is high—perhaps why they wicked better than other layers. “What matters more than how quickly the layer dries is whether a fabric will keep you warm even when it’s wet,” Justin Lichter explained. The Icebreaker material dispersed the moisture across a wide surface area quickly in our tests, so these leggings never felt clammy and did as they should to keep us warm when they were moist from a drizzle or a sweaty climb.

Our testers spotted minor pilling in the mesh areas, but not between the thighs or on the arms, where pilling and rubbing can be an issue. We asked several people who had thru-hiked the Pacific Crest Trail from Mexico to Canada over four to six months about the durability of their Icebreaker bottom. “It lasted me from Mexico to Canada, but it was done after that,” one replied. For most people, this likely translates into many years of use. The other complaint we got from our testers is that initially this bottom felt scratchy or that the fabric made them chafe during outdoor activities. These issues seemed to subside with washings as the fabric became softer.

What to look forward to

Although Icebreaker still sells the version of its BodyfitZone leggings that we tested, the company introduced a new collection of leggings that contain a higher percentage of merino wool in the mesh paneling. These leggings come in a range of weights, from ultralight (150) to midweight (260); we’ll be testing the 200 version this winter. Patagonia has just released its Capilene Air base layers, which contain 51 percent merino and 49 percent recycled polyester. We plan to test these as well, along with new base layers from Ridge, Minus33 (prompted by reader comments left on the men’s version of this guide), and Le Bent. In addition, we’re specifically looking for manufacturers that offer extended plus sizes—something that many of our readers (as well as our own staffers, friends, and family members) have requested.

The competition

Tops

We’ve removed one of our previous budget picks, the Paradox 1/4 Zip Top Base Layer, from this guide as the company’s website shows every model of garment it makes as being out of stock. (We still see a few of the tops available on Amazon, but those may well disappear quickly.) We’ve reached out to the company for more information.

Our previous runner-up, the Ibex Woolies 1 Crew, has been removed from this guide as Ibex has announced an operational shutdown. Although when tested this top performed well in indoor and outdoor environments, had a luxurious feel, and had nice length, we expect it to be widely unavailable very soon.

Arc’teryx Satoro AR Zip Neck Shirt LS Women’s: This stretchy merino-nylon-spandex shirt is the best base-layer top I’ve ever tested because of its exceptional ability to thermoregulate and wick, its flattering fit on all sorts of bodies, and its chafe-free seams. But only half our testers shared my enthusiasm; the rest found the fabric itchy. After back-to-back days of hiking in the San Gabriel Mountains, it felt more durable (and smelled better) than the competition, but even though it was four times the price of our least expensive pick, it wasn’t four times better on the trail.

Duckworth Women’s Maverick Crew: This top would have been a pick if the sizing weren’t so difficult to get right. We loved the fabric: a quick-drying, soft, Montana-grown Rambouillet wool and synthetic blend spun and sewn in the US. Despite a relaxed fit, sizes ran smaller than on almost all the brands we tested. Even after we sized up, the sleeves felt short, and almost all our testers found the arms to be too tight.

Lululemon Swiftly Tech Long Sleeve Crew: This well-fitting top would have been a pick were it not so similar to the less expensive Cuddl Duds FlexFit. This Lululemon shirt wicks sweat away well, effectively fights odor with a silver treatment, and has an articulated torso area that hides a muffin top. Our testers also loved the thumbholes, with their reinforced cuffs, but we found the forearms too tight (I heard “Maybe I just have big arms” more times than seems possible). Reviewers on Lululemon’s website say they are concerned about nicking and durability (and we nicked the fabric 10 minutes into wearing this shirt for the first time).

Uniqlo Women Heattech Crewneck T-Shirt: This fashion top, available in a ton of colors, was almost as good as the Paradox—it’s inexpensive, soft, and very durable—and can also work beyond the outdoors, but its high level of rayon meant the fabric remained wet during sweaty endeavors too long to stay warm. Regardless of our testers’ body shape, this flattering, cheapo layer looked like it fit tightly, but didn’t feel too tight. The fabric was silky soft and very stretchy, not riding up at all when we put our hands above our heads, though the sizing and sleeve length ran short.

L.L.Bean Cresta Wool Ultralight 150 Base Layer Long-Sleeve: This almost-100-percent merino wool top is affordable, functional, and durable. It’s a workhorse shirt that doesn’t have a lot of the flaws that mar other base layers in the same price range, but it also lacks the luxury design features that make the Smartwool tops look so stylish. This merino wool shirt fit well and got the job done for our testers. It’s a good choice for a basic entry-level merino piece.

Arc’teryx Rho LT Zip Neck Women’s: This midweight top was a favorite of OutdoorGearLab, but it was too constricting and expensive to excite our testers, nor did it breathe well. While we liked the sleeve and shirt length, it wasn’t as flattering as the Arc’teryx Satoro AR. The thicker midweight fabric didn’t move well or fit our testers’ bodies in a way that justified the price.

Duofold by Champion Women’s Brushed Back Crew: While this compression-style top looked sexy (with its fun print) and worked for skiing (it’s warm and fleecy soft inside), it was too constricting for other activities and didn’t dump heat well. The sleeve length and shirt length were long enough not to ride up and expose cold spots such as the wrists or the lower back. If you’re choosing between the Hot Chillys and Duofold tops, the Duofold gives you a similar shirt for half the price.

Hot Chillys Women’s Micro-Elite Chamois Crewneck: Testers described the inside of this constricting top to be fleece-like, but the outside felt like neoprene—and seemed to breathe almost as poorly. The midweight fabric also held a plasticky odor that did not disappear after washing. While this US-made Hot Chillys top worked well for skiing in our tests (it’s warm), buyers say in reviews that they find the sizing to run small and that it’s too constricting to be comfortable.

REI Co-op Lightweight Base Layer Crew Top Women’s: This loose-fitting, plastic-feeling top was a disappointment compared with the midweight model, which was our former budget pick and a tester favorite. We didn’t test the midweight model again this time because it didn’t fit into our parameters for a lightweight base-layer top. While this shirt wicked well and was the quickest to dry when wet, the fabric felt cold, even when dry, and the cut was so ill-fitting that our testers left this piece toward the bottom of the pile.

Kora Shola 230 Crew: This base layer was not in the lightweight category we were testing, but we decided to test it because we curious about the yak-wool material. Unfortunately, after testing it, we weren’t quite convinced. It breathed and wicked well; the company says that because yaks live at lower elevations and warmer climates than sheep, their wool regulates a wider range of temperatures better. Yet, unlike the other wool tops we tested, the odor on this one was a bit lanolin-like and unpleasant to some testers when moist, though the odor was not noticeable when dry. The yak wool was also a bit itchy, according to our testers. These offenses would all be forgivable—if it weren’t for this shirt’s high price tag. That pricing may be due to the company’s mission, which is to support Himalayan nomadic farmers through the use of yak-wool cooperatives.

Bottoms

L.L.Bean Cresta Wool Ultralight Base Layer Pants: These bottoms are perfect for someone who wants the anti-stink and breathability benefits of a merino wool bottom without the usual hefty merino wool price. This pair isn’t trying to be anything but long underwear (you shouldn’t wear it by itself), but it layers well under pants except for some bunching behind the knees. It’s a good budget-friendly option.

Lululemon Wunder Under Pant (Hi-Rise): Although this piece is not a traditional base layer, we were crazy about the fit, comfort, and soft fabric, and how well these bottoms stayed up. Originally designed to be worn by themselves for running, yoga, and other activities, these pants also layered well with our testers’ ski and rain pants (and, surprisingly, ski boots), and remained flattering when worn on their own. But these tights weren’t designed to be warm like traditional base layers—and they weren’t for us—so they disappointed us when we tried to stay warm during sedentary activities like watching football games.

Smartwool Women’s PhD Tight: This pair seemed like the perfect set of running tights, but they were too thick to wear under clothing. Otherwise, they fit well and never slipped. They wicked and breathed among the best. They just were too much fabric and warmth to wear as a base layer.

Under Armour ColdGear Armour: With a great fit that stays up, these budget running tights work on their own or as a base-layer bottom. But to our testers, they felt like they had a little too much compression—which is great for reducing fatigue while you’re running, but can reduce circulation when you need to stay warm. More than on any base layer we tested, the color faded after a few months of use.

Duofold by Champion Brushed Back Women’s Pants: These budget tights stretched, wicked, and fit great—except the distance between the crotch and the top of the waistband felt too short. Everyone who tried this pair said they loved it, aside from the fact that it kept falling down. We considered making it a pick because the fit was so good for most testers, especially for the price, but we couldn’t do it because it left the small of every tester’s back exposed.

Arc’teryx Satoro AR Bottom Women’s: This pair was more expensive than our pick at the time of our research, and the fit—while good—didn’t work as well on a variety of bodies. A few testers found the fabric itchy. While these bottoms are an otherwise excellent choice, they just didn’t seem worth the high price to us.

Uniqlo Women Heatteach Extra Warm Leggings: These budget leggings are warm and available in every color. But they had one of the longest drying times of anything we tested, and they didn’t seem to disperse the moisture across a wide surface as quickly as other layers. Add to that a lack of odor control, and we can say that this pair is well-suited for cold conditions when you aren’t working up a sweat, but not for performance.

Duckworth Women’s Maverick Legging: In our tests, this pair’s fit was just too relaxed for it to work as a base layer, looking more like pants than leggings. Our female testers found the rise to be too low, and the distance between the inseam and the top of the pant to be too short. With those problems, plus a thin waistband, this bottom made a plumber out of all of us.

Kora Shola 230 Leggings: Similar to the top, these leggings had an unpleasant wet-wool or lanolin-like smell. They also ran small in sizing. And as with the top, the price on these bottoms was too high to be palatable for most people.

REI Co-op Lightweight Base Layer Tights Women’s: Among our testers, the women found the fit to be off, and all of them noted that the top was pouchy and loose. These bottoms rode high up on the belly button, and several testers found that the waistband was too narrow, digging into the stomach.

Cuddl Duds Climatesmart Legging: These polyester bottoms are very thin and can’t be decently worn on their own. In our tests, they also retained odor more readily than any other bottoms we tried.

Care and maintenance

Although the durability of a base layer depends a lot on its fabric, good care will help maintain the shape and fit of your garment over its lifetime. With the right treatment, a good-quality base layer can last 10 years or more. To maximize your base layer’s longevity, odor protection, and wicking ability, try to wear it as many times as you can before each wash. (On multiday trips, consider hanging your base layers in the sun to reduce odor, which can be just as effective as washing them.)

Minimizing washes isn’t just good for your clothes, it’s good for the environment, too. Pierre Kim of Rhone told us, “The chemicals in [synthetic] treatments often end up in sewer systems and can get into groundwater.” Scientists in 2016 found that microplastics released during washing can end up in the environment. Do your clothing and the planet good by washing your base layers only when they need it.

The washing instructions for wool and synthetic layers are similar:

Wash with similar-colored garments to prevent color bleed. Some garment makers (most notably Icebreaker) suggest that after two or three washes, occasional washing with denim or coarser fabrics can be good for your base layer by helping to remove pilling.

Turn your layer inside out, and make sure the zippers on your layer and other garments that you’re washing with it are totally zipped up.

Do not hand wash—it can create a residual buildup of perspiration, which can lead to odor problems.

Do machine wash. Base-layer makers differ as to whether cold, cool, or warm water is best, but they agree that you should never use the hot wash, which can cause shrinking. Some suggest that gentle cycle is best.

Use a regular, mild powder or mild liquid detergent—not a wool detergent.

Do not use fabric softeners, bleach, or OxiClean. Fabric softeners can coat technical fabrics (both wool and synthetics) and reduce their ability to wick moisture from your body. The chemicals in bleach can reduce the strength of the fibers.

Merino layers tend not to need washing as often as regular cotton clothing. Washing can reduce durability, so washing your merino base layers less frequently is a surefire way to reduce wear. Synthetics need to be washed more frequently, if for no other reason than their higher propensity for odor retention.

Putting your base layer out to line dry or having it lie flat in the shade is the best way to prevent shrinking or melting. Smartwool alone allows tumble drying.

Do not iron prints, labels, or logos on merinos. You should not iron synthetics, as it can melt the fabric. (We’ve seen it happen.)

Backcountry maintenance: While hand washing isn’t the preferred way to clean these pieces when you have access to a washing machine, in the backcountry, it’s a necessity. To follow Leave No Trace backcountry-ethics principles, carry water 200 feet away from a stream using a gallon-size or larger zip-close bag or bucket. Put your base layer in the container along with a small amount of biodegradable soap or no soap at all. Shake the bag or hand wash as you would at home. Hang to dry, preferably out of direct sunlight.

Sources

Justin Lichter and Shawn Forry, the first and only people to thru-hike the Pacific Crest Trail from Canada to Mexico in the winter, phone and email interviews, February 10, 2016